KUALA LUMPUR - The search for Malaysia Airlines flight MH370 entered its fourth day Tuesday. Here is a timeline of the main developments since the Boeing 777 vanished early Saturday with 239 people on board, en route from Kuala Lumpur to Beijing:

SATURDAY MARCH 8

-- Malaysia Airlines says the plane lost contact with air traffic control at around 1:30 a.m. (17:30 GMT Friday), about an hour after take-off from Kuala Lumpur International Airport. Initially, authorities had put the last contact time at 2:40 a.m.

-- Vietnam says the plane went missing in its airspace. It launches a search operation that expands into a huge international hunt in the South China Sea -- now involving 41 ships and 36 aircraft from Southeast Asian countries, Australia, China, New Zealand and the United States.

-- Tearful relatives of the 153 Chinese passengers gather at a Beijing hotel, criticizing Malaysia Airlines over a lack of information.

-- Late evening, Vietnam says its planes have spotted two large oil slicks near the plane's last known location and sends boats to the area, but they find no sign of the plane.

-- It also emerges that two passengers on board were travelling on EU passports that were stolen in Thailand, fuelling speculation of a terrorist attack.

SUNDAY MARCH 9

-- Malaysia says it is probing a possible terror link to the jet's disappearance. The . .sends FBI agents to assist in the investigation.

-- Malaysia says the plane may have turned back towards Kuala Lumpur, for no apparent reason.

-- Late Sunday, a Vietnamese plane spots possible debris in the sea near Tho Chu island, part of a small archipelago off southwest Vietnam. It proves a false alarm.

MONDAY MARCH 10

-- Authorities double the search radius to 100 nautical miles (equivalent to 185 kilometers) around the point where MH370 disappeared from radar.

-- China lashes out at Malaysia, saying it needs to speed up the investigation.

-- In the afternoon Malaysia sends ships to investigate a sighting of a possible life raft -- but a Vietnamese vessel that gets there first finds only flotsam.

-- Chemical analysis by Malaysia disproves any link between oil found at sea and the missing plane.

-- The U.S. Navy sends a second destroyer to join the operation.

-- Boeing experts join the investigation. The U.S. aircraft maker says it is giving technical advice to a team from the U.S. National Transportation Safety Board that is already in Southeast Asia to offer assistance.

TUESDAY MARCH 11

-- Chinese state media report that Beijing is deploying as many as 10 satellites in the hope of finding the jet.

-- The search area now includes land on the Malaysian peninsula itself, the waters off its west coast, and an area to the north of Indonesia's Sumatra island -- all far removed from the flight's scheduled route.

-- Vietnam asks fishing boats off its southern coast -- where the flight dropped off radar -- for help in the effort but says it now holds "little hope of a positive outcome."